The Tofu Interconnect 2

The Tofu Interconnect 2 (Tofu2) is a system interconnect designed for the successor model of the FUJITSU Supercomputer PRIME HPC FX10. Tofu2 uses a 25 Gbps transmission technology that is about two times faster than those of existing HPC interconnects, and uses optical transceivers in an extremely high ratio. Despite the major change of physical transport medium, Tofu2 inherits and enhances the features of Tofu1. This paper describes the specifications including frame format, implementation, and preliminary evaluation results of Tofu2. The effective throughput of Put transfer was evaluated to be 11.46 GB/s that was about 92% link efficiency. The total throughput of simultaneous 4-way transfer was evaluated to be 45.82 GB/s. Tofu2 reduced one-way communication latency by about 0.2 usec. The elimination of the host bus contributed about 60 nsec of reduction, and the rest of the reduction had been derived from the cache injection technique.